This invention relates to a flow cell for a photometer, and particularly to a flow cell for a photometer suitable for a liquid chromatographic detector.
A conventional flow cell for an optical detector comprises a plate-shaped, flow cell body provided with a light path perforation at the center and with a liquid sample inlet passage and a liquid sample outlet passage at both ends of the perforation, and a pair of window members joined at both sides of the plate-shaped, flow cell body, where the flow cell is made smaller in size and the diffusion of liquid sample bands is reduced, as disclosed in Japanese Patent Application Kokai (Laid-open) No. 60-125540.
In the conventional flow cell, no consideration is given to a method for forming the perforation and there is such a problem that a separation efficiency of column effluent components is lowered in the liquid chromatography due to the dead volume or disturbance in the liquid sample flow in the liquid sample flow passages and at joints between the liquid sample flow passages and the light path.
Japanese Patent Application Kokai (Laid-open) No. 60-235041 (=U.S. Pat. No. 4,643,570=European Patent Application No. 0158948) discloses a flow cell (cuvette) comprising two cuvette body halves, at least one of which is composed of a light-transmitting material, the cuvette halves having respective planar surfaces defining the interface between the body halves when the cuvette is assembled, and having recess means in the planar surfaces to define a measuring space as well as inlet and outlet channels communicating with the space. This conventional flow cell has a very small flow cell (cuvette) volume, e.g. a measuring volume of a few nl, a spherical recess having a depth of 3-10 .mu.m at the center, whereas a light path diameter (diameter of the cross section for the measurement beam) of 1 to 3 mm, that is, a shorter light path length in contrast to the light path diameter. In other words, this conventional flow cell has a very low measurement effect.
To improve the measurement effect, the conventional flow cell also proposes to use the reflected light, but use of the reflected light leads to a noise increase, but there is no disclosure of noise reduction in this prior art literature.